1. Field of the Invention
The present invention relates to a monitoring terminal device and more particularly to the monitoring terminal device having a sensor and a wireless communication unit to transmit, by wireless, a monitoring output fed from the sensor.
The present application claims priority of Japanese Patent Application No. 2003-150062 filed on May 28, 2003, which is hereby incorporated by reference.
2. Description of the Related Art
Applications of communications terminals in a communication network typified by the Internet are spreading out from a personal computer and/or a portable cellular phone to an information household electrical appliance. Moreover, by placing various sensors that can observe and monitor a variety of physical quantities in every location where needed in an artificial environment and/or a natural environment and by using information fed from these sensors, it is anticipated that the artificial environment and/or the natural environment will be systematically controlled.
That is, it is expected that a sensor and/or an alarm device placed in the natural environment and, moreover, various sensors and/or alarm devices placed in buildings and/or homes making up the artificial environment will be connected to a network and a monitoring output fed from these sensors and/or alarm devices will be utilized. For example, such a monitoring output can be used for managing temperatures of a paddy field or for detecting a landslide or a like in the natural environment, for checking on an opening or closing state of a window or an operating state of electrical appliances in a household environment, and for checking a state of various alarm devices at an entrance door using a portable cellular phone or a like before going out.
In these sensors, when they are placed in the natural environment in particular, it is desirable that supply of power from the outside or wiring for transmission of information is no longer needed. Therefore, these sensors have to have the same function of transmitting information as a wireless transmitting device, such as a radio transmitter, and an optical transmitter, has and it is necessary that their terminals can operate for a long time without supply of power from the outside.
Technology aiming at reducing power consumption in a non-contact type IC (Integrated Circuit) tag embedding a battery is disclosed in Japanese Patent Application Laid-open No. 2002-42082 (See Pages 3 and 4, and FIG. 6.) in which a sleeping state of a CPU (Central Processing Unit) in the IC tag is changed to its operating state in response to an external trigger. That is, the CPU in the IC tag is ordinarily put in the sleeping state and, only when communication between the IC tag and an external device is required, the CPU is put into its operating state by feeding a trigger to the CPU from the external device.
However, the above-disclosed technology has a disadvantage. That is, in order to receive a trigger from the external device, a trigger receiving section of the CPU has to be always put in its operating state and, as a result, it is impossible to reduce power consumption in the trigger receiving section.